JPH028609Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric soldering iron, and more particularly to an electric soldering iron whose tip is heated by a porcelain semiconductor heating element having positive resistance-temperature characteristics.

In general, heating elements using porcelain such as barium titanate-based porcelain semiconductors or lead-lanthanum titanate-based porcelain semiconductors have resistance-temperature characteristics as shown in Figure 1, which causes a sudden increase in resistance from a certain temperature. It has a sudden resistance increase point (Kurie point) a, the resistance increases as the temperature rises, and after reaching the resistance-temperature characteristic maximum point b, the resistance tends to decrease. Then, this type of heating element is heated to the above-mentioned Curie point a.
By using it as a heating source in the temperature range from to the maximum point b of the resistance temperature characteristic, it is possible to raise the heated object to a predetermined temperature and then maintain it at a constant temperature without using a temperature control device such as a bimetal. can.

By the way, in conventional electric soldering irons that use this type of ceramic semiconductor (hereinafter referred to as a positive temperature coefficient thermistor) as a heat source, the soldering iron tip is attached to the tip of a support fitting that protrudes from the tip of the handle. The heating element is in contact with the outer surface of the tip. However, if the connection between the support fitting and the tip is insufficient, there is a risk that the tip may wobble in the axial and radial directions.
Further, there are other drawbacks such as poor adhesion between the heating element and the iron tip, making it impossible to extract heat efficiently.

The present invention was devised to solve these conventional problems, and its purpose is to ensure a strong connection between the support fitting and the iron tip so that the iron tip does not wobble, and to have a high withstand voltage. An object of the present invention is to provide an electric soldering iron that can improve thermal efficiency and impact resistance.

The present invention improves withstand voltage, thermal efficiency, and impact resistance with a simple structure, and also as a means to prevent the iron tip from wobbling. The soldering iron tip is formed into a cylindrical shape with the electrode part forming the electrode part, and the soldering iron tip consists of a tip body and a press-fitting part that is integrally provided at the base end of the tip body via a flange. The heating element is press-fitted through an electrical insulator into a recess provided in the axial direction from the base end, leaving a space on the inner circumferential side of the heating element, and heat energy is mainly extracted from the outer circumferential surface of the heating element. In addition, this press-fitted part is press-fitted into the support fitting up to the flange position, and a partial deformation process is applied from the outside surface of the support fitting to prevent the press-fitted part from moving within the support fitting. Features.

The present invention will be described below based on an illustrated embodiment.

In FIG. 2, reference numeral 1 denotes a cylindrical handle made of synthetic resin, and a cylindrical cap 2 is fitted into the distal end of the handle 1 and fixed in position via a set screw 3. In addition, the power cord 4 is connected from the rear end of the handle 1.
Cord protector 5 that is molded simultaneously with the
is inserted, and this cord protector 5 is fixed to the handle 1 via a cord set screw 6.

On the other hand, the base end of a pipe 7 made of stainless steel or other corrosion-resistant metal material is inserted into the cap 2, as shown in FIG. Tip 8 is attached.

This soldering iron tip 8 has a cylindrical press-fitting part 8a that is press-fitted into the pipe 7 as shown in FIGS. 2 to 4.
and a tip body 8b which is integrally connected to the tip side of this press-fitting part 8a via a collar part 8c, and two positive temperature coefficient thermistors 9 etc. are inserted into the press-fitting part 8a. It is located. And tsuba part 8c
is adapted to function as a stopper for regulating the amount of press-fitting when press-fitting the press-fitting portion 8a into the pipe 7. Further, from the outside of the pipe 7, as shown in FIG. 4, after the press-fitting part 8a is press-fitted, a partial deformation process 10 such as punching is performed, thereby preventing the press-fitting part 8a from rotating and coming off. It's starting to happen.

Each of the positive temperature coefficient thermistors 9 is formed into a cylindrical shape with a short axial length as shown in FIGS. 3 and 5, and the ratio of the inner circumferential area _S2 to the outer circumferential area _S1 is _S2 /S. ₁ is set to be 0.8 or less. The outer and inner peripheral surfaces of each PTC thermistor 9 are plated with nickel, for example, to form a pair of electrode portions, respectively. Both positive characteristic thermistors 9 are arranged continuously in the axial direction via a donut disc-shaped insulator 11.
A C-shaped cylindrical inner electrode 12 having a slit 12a in the axial direction is elastically fixed to the inner circumferential side by its spring back, and a gutter-shaped outer electrode 13 is wound around the outer circumferential side. Both positive characteristic thermistors 9 are connected in parallel by being pressed together by an insulating sheet 14 provided. From each electrode 12, 13,
As shown in FIGS. 2, 3, and 5, lead wires 16 covered with protective tubes 15 are drawn out, and each lead wire 16 is connected to the power cord via a terminal 17 as shown in FIG. Connected to 4. Further, as shown in FIG. 3, a disc-shaped insulator 18 is arranged at the bottom of the cylindrical press-fitting part 8a.

Next, the effect will be explained.

When assembling, first, two positive temperature coefficient thermistors 9 are arranged consecutively in the axial direction with an insulator 11 in between.
The inner electrode 12 is elastically fixed therein using spring back. As a result, both positive temperature coefficient thermistors 9 are connected together in the axial direction.

Next, an outer electrode 13 is placed on the outer surface of the bipositive thermistor 9, and an insulating sheet 14 is wound around the outer electrode. Then, this assembly is press-fitted and fixed into a press-fitting part 8a in which an insulator 18 is previously arranged at the bottom.
At this time, an axial slit may be provided in the outer circumferential wall of the press-fitting portion 8a to facilitate press-fitting of the assembly. In addition, the outer circumferential surface of the positive temperature coefficient thermistor 9 after press-fitting and the inner circumferential surface of the press-fitting part 8a are connected to the insulating sheet 14.
Pressing may be performed from the outer circumferential surface side of the press-fitting portion 8a so that the parts are brought into close contact with the same pressure at each location.

After inserting and fixing the positive temperature coefficient thermistor 9 and the like into the press-fitting part 8a, the press-fitting part 8a is press-fitted into the tip of the pipe 7 that is integral with the cap 2, as shown in FIGS. 2 and 3. At this time, since the flange portion 8c functions as a stopper, the amount of press-fitting of the press-fitting portion 8a into the pipe 7 is uniformly determined, making the work extremely easy.
Further, since the press-fitting portion 8a is pressurized in the diameter-reducing direction when press-fitting into the pipe 7, the adhesion with the positive temperature coefficient thermistor 9 is improved.

Next, as shown in FIG. 4, a partial deformation process 10 is performed from the outer surface of the pipe 7 to prevent the press-fit portion 8a from rotating and coming off.

Next, the cap 2 is fixed in the handle 1, the cord protector 5 is fixed in the handle 1, the lead wire 16 is connected to the power cord 4, and the soldering iron is connected as shown in FIG. Finalize.

In use, the positive temperature coefficient thermistor 9 is first energized via the power cord 4. Then, the positive temperature coefficient thermistor 9 generates heat in the range from near the Curie point a to the maximum point b shown in FIG.
b, and the temperature of the tip 8 enters a stable state. This is because the resistance of the positive temperature coefficient thermistor 9 rapidly exceeds the Curie point a, and the current is limited.

In actual use, when a heat load is applied, the temperature of the tip body 8b decreases, and the temperature of the positive temperature coefficient thermistor 9 decreases via the press-fitting part 8a, and the resistance also decreases, so that the current increases.

Therefore, the positive temperature coefficient thermistor 9 has the Curie point a
It functions as a non-contact thermal switch nearby.

At this time, the press-fitting part 8a forming the heat receiving plate has an integral structure made of the same material as the iron tip body 8b, and the positive temperature coefficient thermistor 9 is in pressure contact with the press-fitting part 8a, so the thermal efficiency is extremely good and the iron tip body 8b is made of the same material. The tip 8 is quickly heated.

By the way, the range in which a positive temperature coefficient thermistor is generally used as a heating element is the temperature range from the Curie point a to the maximum resistance temperature point b in FIG. It is known that a positive temperature coefficient thermistor can be thermally destroyed due to temperature rise due to Joule heat.

A positive temperature coefficient thermistor with such properties is
Because it is a polycrystalline material made by sintering metal oxide,
The sizes of individual crystals become uneven, and the sizes of grain boundaries between crystals also vary. This means that within a single positive temperature coefficient thermistor there are regions of high resistance and regions of low resistance. Generally, positive temperature coefficient thermistors for AC100V are used with a thickness of 1.5 to 3.0 mm, but when a voltage is applied to a plate-shaped one that is relatively thin and has the same opposing electrode area, In this case, the current density in the above-mentioned low resistance part of the PTC thermistor becomes high, instantaneously causing partial heating, and this part exceeds the above-mentioned maximum point b, making Joule heat breakdown likely to occur. Therefore, conventional positive temperature coefficient thermistors cannot be expected to have a high withstand voltage.

Incidentally, in the cylindrical positive temperature coefficient thermistor 9 according to this embodiment, as well as in the flat plate-shaped conventional thermistor, there are portions of high resistance and portions of low resistance. However, in this positive temperature coefficient thermistor 9, as mentioned above, the ratio of the inner circumferential area _S2 to the outer circumferential area _S1 is
Since S ₂ /S ₁ is 0.8 or less, the area of the inner electrode formed on the inner peripheral surface of the PTC thermistor 9 is smaller than the area of the outer electrode formed on the outer peripheral surface of the PTC thermistor 9. It becomes much smaller, so local variations in resistance no longer pose a big problem.

That is, in a transient phenomenon, when a voltage is applied to the PTC thermistor 9, the current density inside the PTC thermistor 9 becomes higher than the current density on the outside due to the difference in the area of the inner and outer electrodes, and the current density increases in the radial direction. A difference in current density occurs. This means that heat gradually spreads from the inside to the outside, and there is a time difference in heat generation in the radial direction of the PTC thermistor 9. In other words, the ring of high resistance expands from the inside to the outside. For this reason,
When the resistance on the inside is near the maximum point b in FIG. 1, the outside has not reached the maximum point b, and when the resistance on the outside approaches the maximum point b, the positive temperature coefficient thermistor 9 as a whole is below the maximum point b. It enters a stable state at .

To explain this in more detail, in a positive temperature coefficient thermistor, the current is controlled by the temperature of the positive temperature coefficient thermistor. By the way, in a flat positive temperature coefficient thermistor, the temperature rises and falls at various points in the plate thickness direction at the same time, so the current is not limited unless the entire positive temperature coefficient thermistor is heated to a certain temperature. For this reason, if there is a portion with low resistance, a large current will flow through the portion with low resistance before the temperature of the entire device rises to a certain level, making it easy for Joule heat damage to occur.

On the other hand, in the case of a cylindrical positive temperature coefficient thermistor, as mentioned above, the ring of high resistance expands from the inside to the outside.
Even if the temperature of the PTC thermistor as a whole is not that high, the current inside the PTC thermistor begins to be restricted. For this reason, even if there are parts with small resistance,
A large current is restricted from flowing through this portion, making it difficult for Joule heat damage to occur.

Therefore, local variations in resistance inherent in the positive temperature coefficient thermistor 9 do not pose a problem, and even when a high voltage is applied, it becomes difficult to exceed the maximum point b, and Joule heat damage is effectively prevented. Therefore, it can be used from low voltage to high voltage.

Note that even if the positive temperature coefficient thermistor is cylindrical, the ratio of the inner circumferential area _S2 to the outer circumferential area _S1 is
When S ₂ /S ₁ is 0.8 or more, the difference in the area of the electrode parts formed on the inner and outer peripheral surfaces becomes smaller,
Therefore, the difference in current density between the inside and outside is also reduced. For this reason, the effects described above cannot be fully expected.

FIG. 6 compares the voltage-current characteristics of the cylindrical positive temperature coefficient thermistor 9 according to this embodiment and a flat positive temperature coefficient thermistor with the same composition and thickness and the same opposing electrode area. It is a thing,
In the figure, characteristic A indicates the PTC thermistor 9 according to this embodiment, and characteristic B indicates the conventional flat PTC thermistor.

As is clear from FIG. 6, it can be seen that the positive temperature coefficient thermistor 9 according to this embodiment can be used up to a higher voltage than the conventional flat thermistor without causing Joule thermal breakdown.

As explained above, this embodiment provides the following effects.

(1) The press-fitting part 8a is press-fitted into the pipe 7, and the pipe 7 is partially deformed 10 from the outside surface, so the tip 8 and the pipe 7 are firmly connected and can be used for many years. Even if you do so, the tip 8 will not shake.

(2) Since the flange portion 8c acts as a stopper when press-fitting the press-fitting portion 8a into the pipe 7, it is easy to fix the insertion position of the tip 8 during assembly.

(3) The positive temperature coefficient thermistor 9 is in close contact with the press-fitting part 8a, and heat is directly transmitted to the tip 8. Moreover, since it is arranged inside the press-fitting part 8a pipe 7, the amount of heat dissipated from the press-fitting part 8a is small, so thermal efficiency is improved. is good.

(4) Unlike conventional ones, the positive temperature coefficient thermistor 9 is not exposed to the outside, so it has excellent impact resistance.

(5) Since the withstand voltage can be improved, there is no need to manufacture each separately according to the voltage used.

(6) Since both positive characteristic thermistors 9 are arranged in parallel in the axial direction, the electrodes 12 and 13 can be easily processed.
In addition, the inner electrode 12 causes a bipositive thermistor 9.
Since they are connected together, assembly is easy.

(7) Since both positive temperature coefficient thermistors 9 are electrically insulated by the insulator 11, there is no problem even if the contact resistances between the electrodes 12, 13 and each positive temperature coefficient thermistor 9 are different from each other.

As explained above, in the present invention, a heating element composed of a positive temperature coefficient thermistor is formed into a cylindrical shape in which the outer peripheral surface and the inner peripheral surface form the electrode part, and this heating element is provided in a press-fitted part. By press-fitting into the recess, leaving a space on the inner circumferential side of the heating element, heat energy is mainly extracted from the outer circumferential surface of the heating element, improving withstand voltage without changing the composition or thickness of the heating element. Thermal efficiency and impact resistance can also be improved. In addition, since the press-fitting part is press-fitted into the support fitting and thermal expansion in the radial direction is restricted, the outer circumferential surface of the heating element and the inner circumferential surface of the recess are always in close contact with each other, further improving withstand voltage. Can be done.

In addition, the press-fit part is press-fitted into the support metal fitting up to the flange position, and partial deformation is applied from the outside of the support metal fitting, making it easy to position the tip and ensure long-term use. There is no risk of the iron tip becoming loose.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the resistance temperature characteristics of a positive temperature coefficient thermistor, Fig. 2 is a sectional view showing an embodiment of the present invention, Fig. 3 is an enlarged view of the main part of Fig. 2, and Fig. 4 is a graph showing the resistance temperature characteristics of a positive temperature coefficient thermistor.
5 is an exploded perspective view showing the relationship between the PTC thermistor and the electrodes; FIG. 6 is the voltage-current characteristics of the PTC thermistor according to the present invention and the conventional PTC thermistor in the form of a flat plate. This is a graph showing a comparison. 1...Handle, 2...Cap, 7...Pipe,
8... Soldering tip, 8a... Press-fitting part, 8b... Soldering tip body, 8c... Flange, 9... Positive characteristic thermistor,
10...Deformation processing, 11, 18...Insulator, 12
...Inner electrode, 13...Outer electrode, 14...Insulating sheet.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A supporting metal fitting is provided protruding from the tip of the handle, a soldering iron tip is attached to the tip of this supporting metal fitting, and the soldering iron tip is heated by a ceramic semiconductor heating element having positive resistance temperature characteristics. In an electric soldering iron that heats, the heating element is formed into a cylindrical shape with an outer circumferential surface and an inner circumferential surface forming an electrode part, and the tip is connected to a tip body and a base of the tip body. The heating element is press-fitted into a recess provided in the axial direction from the base end of the press-fitting part through an electrical insulator, thereby forming a heat-generating element. The inner circumferential side of the heating element is left as a space, and the heat energy is mainly extracted from the outer circumferential surface of the heating element, and this press-fit part is press-fitted into the support fitting up to the flange position, and a partial section is removed from the outer surface of the support fitting. An electric soldering iron characterized by performing deformation processing to prevent a press-fit portion from moving within a support fitting. 2. The electric soldering iron according to claim 1 of the utility model registration claim, characterized in that the area of the electrode portion on the inner circumference side of the heating element is 0.8 or less with respect to the area of the electrode portion on the outer circumference side. .